calibration and quality control Flashcards
what is calibration
process proving link between nstrument signal and concentration of the anayte
ensues results obtained on local analyser match defined reference method
what is an assay working range
senstivity, minumum amunt of analyte distinguishable and its upper limit before exhaustion
when is single point calibration used
with a linear working range
sample blank
no sample but only reagents
want to measure everything above the backgrund
heterogenous analytes
mixture of releated molecules
traceability
an unbroken chain of comparisons of measrements leading to a known reference value
primary reference procedure
fully understood procedure of highest analytical quality
seconddary reference methods
uses in hopsitals to measure concentrations in secondary samples
outline process of calibration
master calibrant mde by manufactuers
this is measured by te AAS method
assat calibrated using secndary calibrant
this then referenced against secondary reference procedure
then caloibrated with pure analyte
then measured by primary calibratory which everything in the world is calibrated against
ICQ
internal quality control
assurance that results are comparable to the previous days an everything is accurate
patient means should be steady
types of assay erry
- large changes in bias due to calibration or reagent error
- slow drift in assay results from age of reagents or equipment
internal QC controls
minimal vial to vial control variation
eg dont use the same manufacturers control and machine as there could be errors
how should new QCs be handled?
calibrants run in with old one to check for a differene
determien mean and SD of results and check for rejection rules: westgard rules
whats rejected on a control chart?
any mean below -3SD
what is external quality assesment
provides assurance that resultsare comparabe between laboratores
documentation of long term performance
whats the role of lboratory accreditation
ensure procedures are in line with legistaltion and best practice
involves inspectios and standards
total quality management
planning lab practice control inernal and external aassurance imporovements
analytical sensitivity definition
detection limit of the experiment
the smallest amount of material that the experiment can detect
analaytical specificity
referes to if any other similar chemicals will interfere with the test
what is POCT
point of care testing
- bedside, near patients extralaboratories and decentralised tesitng
examples of POCt
urine dipsticks
pregancy estses
diabetets blood tests
role of mini-analysers
small intruments to carry out focusses tests in A and E or intensive care units
- RBC/WBC counts, troponin in heart attacks blood gasses and drug abuse
what is a microanalysers
singe analysis on a single sample
found in A/E and ICU
eg rapid test for Ddimers in a pulmonary embolism
benefit of POCt
speed and ease of diagnosis
easy intervention
decreases doctor time with patients
efficient management of patients
